Recent research has brought a powerful spotlight on not just the ecological, but the overall, importance of sea cucumbers to the environment. Sea cucumbers occur all over the world and at all depths. Often, when present, they are abundant or at least a significant part of the fauna present.

But the key dynamic present to their importance is that they cycle or process what they eat and what they defecate contributes to the health of the habitat they inhabit.

I realize that articles about "coral reefs saved by sea cucumber poop" sound kind of silly on the surface, but read and understand below.... (note also the Journal of Geophysical Research? Important stuff gets put in there.)

Coral has to develop or accumulate calcium carbonate, which is the mineral used to compose coral skeletons, at an equal or better than the rate at which the coral loses calcium carbonate via erosion, natural dissolution, etc.

A survey of the sea cucumbers Stichopus herrmanni and Holothuria lecuospilota in One Tree Reef, Australia showed that the sea cucumbers could digest and dissolve so much of the adjoining sediment and rubble (ie the sand) that they actually contributed up to 50% or MORE of the total amount calcium carbonate dissolved over a night time. Presumably this was made available for coral to use for reef development.

Chemically, calcium carbonate is very alkaline or basic. So, sort of like an antacid. What do you do when you have stomach acids that are misbehaving? Drop some of those tablets to "cancel" out the acidity.

So, sea cucumbers contribute calcium carbonate to the coral reef's "chemical budget". They act like a natural antacid to neutralize other acidic environmental sources. Under normal conditions, there's an equilibirum. The abundance or number of sea cucumbers can affect this.Thus, in theory, MORE sea cucumbers might produce so MUCH alkalinity (or "basic" poop to the water) that conceivably they could function as a control or at least a buffer against increases in more acidic sea water. This obviously is important when you consider ocean acidification resulting from global warming. Sea cucumber poop is an important part of helping to keep the geochemical balance of a coral reef in equilibrium.

2. Sea Cucumbers EAT tasty bottom poop and clean it up! Poop is processed into useful nutrients! Over abundance of nutrients (i.e eutrophication) is broken up by sea cucumber feeding!

MacTavish and his colleagues studied a nutrient-rich environment covered by algae, mussel feces and other nutirent-rich goodies. Under normal circumstances, these would build up bacteria, ammonia and other factors creating conditions that contribute to the growth of algae, which ultimately chokes everything else out (aka eutrophication).

But you put a sea cucumber into these settings? They LOVE it! They eat and all sorts of good things happen:

Bacterial abundance increases

Organic material (i.e., the goo) begins to decompose more quickly

Organic materials are redistributed from the marine sediments into the water

Sea cucumbers help to break down organic material and redistribute the nutrients! The poop is an important part of that process.

Eutrophication-the overabundance of nutrients resulting in undesirable growth of algae and hypoxia-is a common problem in aquacutlure ponds.

Image by Smartfish-ioc

But putting a sea cucumber into the mix? A critter that LOVES organic nutrients and gooey stuff like that? It would go to town! Cleaning up the bottom and cycling those bottom nutrients... Seems like a win-win solution for cleaning up the bottom of say a fish or mussel farm where feces from the animals accumulate in huge amounts.

So yes. Sometimes sea cucumbers eat poop. And then poop poop, which is probably "cleaner" than what went in the first place...

4. Sea Cucumber poop is good for plants (mangroves, seagrass, etc.), which are part of a healthy ecosystem

Image by Eunice Khoo- "Mermate"

So, by this I don't just mean ONLY the poop-but the animal digesting and then processing the sediment. This follows everything from the above-they break down organic detritus and make the nutrients available to the water column preventing hypoxia and other bad things going down in the sediment...

Think of them as earthworms! go through the bottom sediments, eat all the organics and leave the sediment.. that's sea cucumber poop!

5. Deep-Sea Cukes have pretty diverse microbial faunas that live in their guts! (and thus their poop!)Deep-sea sea cucumbers perform very much the same kind of function as the shallow water ones. They live in much finer mud and are often rained upon by nutrients from the surface. Many of these critters, such as Molpadia (shown here) live buried in the mud.

Seriously! This is one of the top images that comes up in a Google search for "brooding"

I meant Brooding juveniles like THIS!

from the Smithsonian NMNH USARP

In other words, these are "baby" starfish that are cared for by the mother until they are ready to head off ont their own. Parental investment resulting in a succesful offspring.

Sometimes starfish (and indeed most echinoderms) can appear kind of alien. No head. Mouth on the bottom. 5 part radial symmetry. Strange adaptations. All kind of weird sometimes.

So, I suppose its appropriate that the WEIRDEST of ALL echinoderm (and starfish) behavior is that starfish have this almost mammal-like (or at least, vertebrate like) behavior!! Some starfish species will actually brood and carry little starfish just like the cutest little furry thing you can think of!

But many starfish species stray from that typical cycle, and somewhere between the time the sperm fertilize the eggs and the settled "babies" are established the whole life cycle CHANGES to give you this:

Yes. Tiny baby or small juvenile starfish which are held by the mother around the mouth! (this varies as we'll see). Why do some starfish do this? And not the more 'typical' behavior?

Scientists have known about brooding behavior in several species of starfish since the 19th Century but only recently has there been the extensive observation and insight to finally piece together the complete story!

Hamel and Mercier's paper exhaustively studies L. polaris' complete reproductive cycle, which pretty thoroughly documents the reproductive behavior in this species. Bear in mind, that this starfish has been known since 1842 and yet our knowledge of its reproduction has only come to us recently (published in 1995)!

Information on brooding remains of interest-but the behavior and its evolution is poorly understood.

1.PSEUDOCOPULATION

Figure 1 from Hamel & Mercier 1995

As a prelude to the actual spawning there are massive aggregations of these animals. They're involved in an unusual behavior known as pseudocopulation. There's no penetration or combination of sexual organs, nor is there any actual spawning. The animals all just get together into a big pile. Sort of preparation for the main event.

Bear in mind, OTHER than during mating season (November to February), these animals all typically ignore or even avoid one another.

Many echinoderm species practice pseudocopulation which I've written about here. Its not always clear why different species pseudocopulate. But one thing seems clear: It helps the chances of their sperm and eggs get together.

Here (from Figure 5 in Mercier & Hamel) we see a close up of eggs UNDER the female in C. Which then grow up into the cute as the dickens starfish in D. Growth was after about 5 and half months.

4. After fertilization, development proceeds. Here's a summary panel of the different stages. The top row is the developing embryo. It continues through different stages until it reaches "J."

At that point the animal is practically ready to move off on its own..

Figure 9 showing development from embryos to small starfish

Interestingly, Hamel & Mercer found that the development proceeded on its own if the embryos were unbrooded. They suggest that brooding is behavior which protects the embryos/juvenile starfish from debris and other materials. Animals observed in the field were clear of excess materials.

Protection was also a likely consideration since unprotected embryos/juvenile starfish were rapidly devoured by sea urchins or other grazing animals if they were not protected by the adult.

The whole cycle is sumarized in this convenient cartoon!

Figure 4 from Hamel & Mercier 1995

There were MANY more details! If the topic of brooding interests you I urge you to check it out!

BUT That's NOT the end of it!

5. Brooding is diverse. SEVERAL different species of sea stars brood. Almost all of them are either cold-water species, living in the deep-sea or at the poles. Sometimes brooding is in temperate water species.. But typically not in the tropics.

Brooding also takes different forms. The oral 'mouth' or gastric brooding mode is but one kind. Here is Diplasterias from the Antarctic! MANY starfish in the Antarctic brood juvenile starfish!

For those who are not familiar, tunicates are actually members of the same overall group to which humans and all other vertebrates belong! A subgrouping, called the Tunicata within the larger phylum Chordata. Honestly, the relationship is pretty basic info which you can find with a quick Google search

Most times, tunicates are small, out of the way or encrusting (i.e., covering surfaces over a wide area) but can be very abundant, carpeting areas until nothing else grows there..such as this one (Botrylloides diegensis) which is an invasive in San Francisco Bay from Asia.

Image by Luis A Solórzano, KQUEST

Under many conditions, tunicates are ugly and kind of bland colored things that are common components of fouling communities. Its species such as this one which earn the oh so lovely common name "sea pork"(Amaroucium californicum). And so, they get a bad rap.

image by Jkirkhart35

But tunicates are often gorgeous and attractive animals. PLUS, they do weird and unusual (if kinda creepy) things! Let's go see!

1. Some BasicsThis shows two siphons: one is where water goes IN and the other is where it goes OUT.

Image by Arne Kuilman, from Anilao, Philippines

Food gets caught in the "Pharyngeal basket" (=the "filter" for its filter feeding) where it gets moved down to the stomach. A pretty simple overall anatomy. But note, it has well-developed organs that you would find in a proper animal. This is important later...

This gives you a general idea of the animal as a whole (not sure if this is the exact same species but you get the general notion)

Image by Prilfish

Basket Close ups!

Image by Steve de Neef

Cross section! the space between the 'tunic" and the feeding basket

Image by "stupidhead"

Image by Star Tsai

INSIDE the basket!

Image by Eric Cheng

Image by Christian Loader

Image by Steve de Neef

2. Some Diversity... Some tunicates are individuals

Image by bybegone

Whereas other forms are colonial...

Image by Patrick Nilsson

Botrylloides magnicoecum from Australia. And yes, those are apparently the REAL colors.

Image by Leander Wiseman

Botrylloides leachi from Australia

Image by John Tumbull

Fantastic image by Pat Sinclair

Other tunicates are more....unusual in appearance (I think these are solitary) BEHOLD! Sea Tulips! Pyura spinifera from Australia!

Image by Richard Ling

Here's only a few...

Also by Richard Ling

Here's a LOT of them

Image by Richard Ling

Another stalked tunicate, Oxycorynia fascicularis from Anilao in the Philippines

Image by Optical Allusion

Stalked GREEN tunicates! Same species? Oxycorynia fascicularis

Image by Mer Mate-Eunice Koo

And although I've been focusing on shallow water, I can't get past tunicates without the obligatory showing of the famous DEEP-SEA predatory tunicate (Megalodicopia hians)!! The IN siphon is modified into a mouth and the OUT siphon kicks out the tunicate poop! Let's let the British narrator take us away!

3. The predatory tunicate is a great segue for the vice versa! People EAT tunicates.As I've outlined here. Its called the "sea pineapple" among other things in Asian cultures, but different species (called 'sea violets') are eaten by Europeans..

Image by sjbutterfield2

MMmm........tunicates and kimchi....

Image by Mark Deibert Photography

4. Tunicates are a little creepyIf tunicates have similar enough tissues (historecognition) ie. are similar enough two physically different individuals can physically FUSE together.Why say it, when you can SHOW it?

the description from the video:

This video shows a fusion event in progress between compatible individuals of the sea squirt, Botryllus schlosseri. At the beginning, terminal parts of vasculature, called ampullae, which surround the colony, have come into contact (one colony is on the top right, the other on the bottom left, out of the field of view). The ampullae push into each other repeatedly, and finally the cell layers between two ampullae fuse, and results in both individuals sharing a common circulation. Fusion can best be seen on the top left, but occurs in several places in the region of interaction. The decision to fuse or reject is based on whether the two colonies 'match' each other, analogous to how humans accept or reject transplants.

Sponges don't have tissue, so those videos where they grind em' up and they get back together?

Not that hard for animals that are still essentially just colonies of cells. Proper ANIMALS with tissues don't typically do stuff like that. The fusion shown in tunicates above? That's like you and your family, suddenly fusing into one big amorphous pile. Squicky, eh?

Urchins feed primarily with a unique jaw-like structure known as Aristotle's lantern. It looks like this in most urchins but is modified in so-called "Irregular" urchins such as sand dollars, sea biscuits and etc. A bit about this here.

Here is the jaw in action, with the tips being extended from the mouth as the animal rasps away on the bottom it lives on...

Believe it or not. Sea urchins have among the most diverse feeding modes within the Echinodermata. Here is a roundup... COUNTING DOWN!

5. Herbivores and GrazingThis is the one everybody knows about and the feeding mode with which most people are most familiar. Many sea urchins prefer kelp and various other seaweeds and marine "plants." There are several species found in cold-temperate water habitats.. California, New Zealand, Chile.. to name a few, and all these places have sea urchin species in abundance.

Here is the famous purple sea urchin, Strongylocentrotus purpuratus engaged in some kelp feeding!

Image by Todd Jackowski

Urchins are ecologically important in kelp forests. Removal of predators (and control of the population) can lead to a circumstance known as "urchin barrens" where sea urchin abundance goes out of control. In those circumstances, even sea urchin poop can become a serious consideration (here)

Note that while many sea urchins feed primarily on kelp, they are not obligated to do so. Their diet permits them some nutritional flexibility.....

4. Omnivory and Scavenging

Most people (even several biologists) don't realize that sea urchins can be pretty flexible in their diet. If kelp isn't available, they will obtain whatever nutrition happens to be available.

Some large examples of food here, but feeding also includes microalgae (such as diatoms), encrusting algae, moss animals (i.e. bryozoans) and etc.Here we have what Strongylocentrotus spp. in the Arctic or sub Arctic feeding on what looks like a wayward or moribund jellyfish..

Image by Alexander Semenov

And in the tropical Indo-Pacific (Lembeh, Indonesia), Astropyga radiata is feeding on some nice dead fish (and who doesn't like a nice dead fish every so often?)

Image by Christian Loader

Up until recently though, feeding in sea urchins has been thought to be relatively passive and opportunistic. Whatever comes along is good to go!

Most people don't think of sea urchins as aggressively chasing down and pursuing ACTIVE prey...

This notion was recently shown to be incorrect...

3. PredationProbably one of the most dramatic deep-sea/paleontology events in the last few years was the discovery that, not only could stalked crinoids (echinoderms with a ring of feeding tentacles and a stalk) crawl BUT they did so with some urgency!

2. Deposit Feeding/Sediment FeedingWhew! That was quite a violent section for sea urchins, wasn't it??? Let's go to something a bit more majestic!One of the NEATEST stories in sea urchin evolution is how a major sub group, the "irregularia" aka the sand dollars, sea biscuits, and spatangoid ('heart urchins') sea urchins all evolved from a more open lifestyle with the feeding modes shown above (herbivory, predation, omnivory) to a specialized series of body forms that involve plowing through sediment/mud/sand in order to obtain food. Deposit or sediment feeding. A more involved post of this story can be found in this post.

Feeding in these animals is intrinsically connected with their life mode and body shape. Here are some videos that show some of these animals plowing through sand...sometimes just to get around but maybe also to feed?

Japanese sand dollar plowing through sand...but check out the food going to the mouth at 1:05.

Note all the spines moving through the sediment...

Again.. check out the spines!

1. Filter/Suspension FeedingSo, now that I just got done telling you that sand dollars and their relatives are deposit feeders.. I will immediately point out the exception! Perhaps the most UNUSUAL feeding mode in sea urchins is filter feeding, i.e., obtaining food from water currents using some kind of sieve or screen.

Urchin morphology tends to be...counterproductive where this sort of feeding is concerned.. Except in TWO unusual examples.....Dendraster excentricus-is the so-called "Eccentric Sand Dollar"which lives along the west coast of North America. So named for the very erratic pattern of its feeding grooves on the oral surface.

Image by fiveinchpixie

Image by Peter_r

Note an oddity in its feeding posture.. these animals are tilted at an angle into the water current standing on its "side" in the sand. Other sand dollars such as the ones listed under #3 lie flat on the sandy bottom.Dendraster uses its tube feet, pedicellariae and spines to pass along food caught from the water currents to the mouth.. More info on this species to be found here.. This is a pretty commonly encountered animal, but really when you look at them in this fashion, they are freaky deaky!

Dermechinus horridus So yes. Saved the BEST for last!

Dermechinus horridus is a strange deep-sea sea urchin which has a body, literally shaped like a cactus, with sharp, needle-like spines to boot! It is among the oddest of the sea urchins known.

Tribbles are actually a GREAT introduction for today's topic: SEA URCHIN BARRENS!

What are Sea Urchin Barrens?? These are places where a sea urchin species' abundance increases dramatically to the point where the urchin devours EVERYTHING in its path, effectively leaving all else 'barren' except for more hungry sea urchins.

Image by Annie Crawley

Images above by AndyOlsson

This is not far removed from the imagined "ecology" of Star Trek's tribbles (A good essay applying real population math about tribble populations can be found here, but this image from the famous ST:TOS episode hopefully gives you the general idea!)

The gist of it is simple: TOO MANY URCHINS and they EAT TOO MUCH. But unlike tribbles (which were eradicated by Klingons-yes I know they're not real), in the case of sea urchins, we can actively study the ecological interactions and conditions which have caused the populations to explode in number.

Image by AndyOlsson

Here is a video showing tons and tons of Red Urchins (S. franciscanus) on a barren in Southern California. Thee bottom is essentially devoid of all but more hungry urchins!

What causes urchin barrens? Um. Its complicated but the common thread seems to be that there is an association between barrens and the absence of sea urchin predators.

In one of the most familiar studies from the Pacific Northwest coast, the main predators were sea otters (in many cases, I assume Enhydra lutris-some papers did not mention species).

The fundamental ideas outline the notion that as sea otter populations decline, predation pressure decreases and with nothing to keep the populations at a controlled level sea urchin populations dramatically increase and began to devour kelp (and really everything else!) to the extent that they effectively clear the bottom.

Image by Santa Monica Bay Restoration Foundation

Image by Annie Crawley

In Stewart & Konar's paper, individuals from these population explosion urchins were compared against "healthy" urchins which occurred naturally in kelp forest habitats. Some dynamics:

Urchin densities were SEVEN times greater than those elsewhere

Kelp forest (vs. 'barren') urchins were larger and more robust

"Barren' urchins were smaller with less tissue

"Barren urchins had little to no reproductive tissue compared to kelp forest urchins

Different species of Strongylocentrotus (as well as other urchin species!) live in different places and have different predators!

On the North Atlantic coast, there is a similar population explosion of the Green Urchin, Strongylocentrotus droebachiensis, which from the look of it, is pretty severe

Some, such as this paper, have proposed that these population increases have been caused by the loss of lobsters (Homarus americanus) which feed on green sea urchins. But in all liklihood, as the system is better understood the more complicated the explanation.

Image by AJmart

Other predators, such as wolf eels and starfish, also feed on green sea urchins and well.. it can get messier...

Now, in the Southern Hemisphere we have a similar, parallel situation with a completely different family and species of sea urchin: Centrostephanus rodgersii (Diadematidae).

The range of the urchin is dramatically expanded because of increasingly warm waters in/around the eastern Tasmanian region.

The lobster Jasus edwardsii is one of the primary predators of Centrostephanus and has been heavily overfished. The BIG lobsters that would feed on urchins are taken for food leaving the urchins to run amok!

Its important to note how significant the human factor has played into these dynamics. Climate change and overfishing are thought to be the primary agents responsible for urchin "barrens" in these circumstances.

This issue has been conveniently summarized in this video...

The takeaway lesson:Predator loss seems pretty strongly associated with urchin "barrens" aka population explosions. But all sorts of environmental factors, including warmer waters, and multiple predator interactions can be important..So we have a LOT of sea urchins. Couldn't we uh..just eat them?

Yes.

BUT, you can after all, only fish so much. After you've taken the lobsters, the urchins and the kelp what else have you got left? A good answer seems to lie with good sustainable fisheries management..but we shall see how this works out...

People are always fascinated by how animals eat and, I think, the weirder the better. Starfish have one of the most distinctive feeding modes of all animals and I think, that's why people get fixated on how they consume their prey.

Most of these species occur in a primary range of about 500 to 1500 meters, but some can get relatively shallow. Most are difficult to study and live on the deep-dark sea bottoms...

2. Figuring out feedingThere's generally TWO ways to study feeding:

Directly: i.e., you watch a species consuming its prey (or whatever food) and voila! You have a direct feeding observation.

Indirectly: You have something which provides inference about what the animal has already consumed. Look at the gut contents or something similar...

In the old, old days, figuring out the feeding ecology of deep-sea species was difficult. Specimens were collected via net-and usually brought up badly damaged. The animals were mostly dead and had often emptied all of their gut and stomach contents. Rarely did you have an opportunity to see the animal interacting with any possible prey items. Any interactions you might have spied could have been caused by the trawl net scooping up any and all of the bottom fauna...

In contrast, I think Ms. Gale et al's paper has acquired some great information using some modern techniques and good ol' fashioned detective work!

Direct Observation So, the most obvious and direct way to observe feeding is by watching it! These days, submersible robots aka ROV's (Remotely Operated Vehicles) are one of the main platforms for these types of observations. I've done some similar work in the Pacific (here)

Fig 9A from Gale et al. 2013

This is Hippasteria phrygiana, a widely occurring cold-water/deep-sea coral (and cnidarian) predator, but Gale et al. observed several other species from the deeps, about 500-1100 meter depths, of the North Atlantic.

used their tentacles (which all have stinging cells) as a defense against the oncoming hunger dogs! And this was effective against the more timid Ceramaster but not against Hippasteria. Flabellum was fed upon by Hippasteria VERY quickly (in 18 minutes)..

Indirect Evidence. This is where some newer techniques shows us some cool ecological stuff!!

In doing so, they become kind of like a "fingerprint" for a particular kind of ecological role. So, for example, species with a stable isotope N (Nitrogen) value of about 16, but w/ Carbon value of about -14 (Hippasteria, Ceramaster and Mediaster) are higher within the overall trophic relationship among these asteroid species.

Fig. 6 from Gale et al. 2013

You've seen Hippasteria, but here's Ceramaster granularis

Image by EIN _LEIK

and Mediaster bairdi

Image by K. Gale

All the other species, including Novodinia americana, Leptychaster arcticus, Ctenodiscus crispatus and Zoroaster fulgens display lower values which would be consistent with their previously thought of feeding modes as suspension feeder (the brisingid) and deposit feeders/detritivores (mud stars, including Leptychaster and Ctenodiscus) and Zoroaster.

Gut Contents & Prey Items!One other indirect way of looking at food items? Gut contents. What were they eating?

Ms. Gale did a LOT of work looking through the guts of many starfishes.. Much of how they fed is based on detective work. For example, many animals such as deep sea gorgonians and such, after being digested leave only skeletal bits called sclerites.

Fortunately, these can be used to identify the animals with some accuracy. Curiously Hippasteira also had some crustaceans in its gut..

Figure 3 from Gale et al.

One of the subject animals, Zoroaster fulgens has been one of the more mysterious deep-sea starfish species in my experience is an infaunal predator, that is, a species which eats animals living in bottom mud and sediments. A related zoroasterid called Doraster is shown here with a snail in its mouth with snail food in the red circle

Gale et al reiterate the importance of the feeding ecology of many of these species...

Suspension feeding asteroids such as Novodinia capture food from the water column that would ordinarily not be made available to bottom feeders

not N. americana. Image by NOAA National Ocean service

I've recently discussed some recent observations of a seemingly innocuous species, Porania pulvillus as a predator rather than a passive ciliary feeder. Understanding deep-sea ecosystems is an exciting endeavor, who knows what we'll find! Simple things like feeding are intriguing and interesting-but poorly known. What will the important impacts of these species be down the line?

But even BASIC knowledge such as this is a complex and time-intensive process. It starts with work like this...

The Scanning Electron Microscope (SEM) is a wonderous device. Simply put, electron beams provide a highly detailed almost surreal image of the surface they are directed at.

But what happens we direct an SEM at animals that are ALREADY kind of weird? The striking beauty of sea urchins is revelaed!

The sea urchin skeleton. Also known as a TEST. One of my many regularly repeated caveats- these are NOT shells. These are underlying skeletons which have a layer of skin which is typically removed to reveal the more aesthetic skeleton...

Here is an example from a cidaroid sea urchin.. Those round knobs or bosses? Those are where the spines articulate with the body...

Image by Gripspix

Here's a nice macro shot of aforementioned "boss" (=the knob which connects with the spine).

Image by "Nervous System"

But what happens when we focus a Scanning Electron Microscope (SEM) on these surfaces? (note that these images are a different species from the one above).

Here's one that shows not only the spine "bosses" but also the sieve plate aka the MADREPORITE on a sea urchin. See that really porous plate (the one with all the black dots) in the right hand corner??

The Okeanos Explorer has been to Indonesia and many other locales, such as the Galapagos and the deeps off the Caymans, but is currently operating off the east coast of North America, surveying and studying a series of deep-sea canyons and seamounts as seen here. Those on the legs I've seen (2nd leg?) are in white arrows...

What's even more fantastic? Many deep-sea biologists, some world experts in the field, are actually listening in via phone, or via internet forums. I'm one of the world's experts on starfish and I'm monitoring via Twitter (@echinoblog) and via conference call.

Each day of the expedition can go anywhere from 5 to 7 hours. So there's a LOT of footage. So here.. I present some of the highlights of new discoveries and neat, weird deep-sea animals from the last few days of video footage.

There's still more to come and undoubtedly, I've undoubtedly missed some but this gives you a nice overview of new discoveries and awesome stuff from the 1000+ meter deeps off the east coast of North America!

These animals are heavily studied and are important to ecologists as well as physiologists and even scientists researching astrobiology (those that explore how life on other planets originated in extreme habitats)

Cold Seep habitats are unusual and when found, they are often monitored by the scientific community for study because of their potential importance.

Parasites? Commensals Part of the animal? A new species? MANY questions!

Sea Spiders aka Pycnogonids crawl on deep-sea corals and other cnidarinsHere's one on a sea pen

Another crawling on some deep-sea coral

Weird & Rarely Seen Deep-sea starfish species!This starfish, called Pythonaster, is known from fewer than 6 specimens in the entire world. This is the 2nd time this animal has been observed alive and the FIRST time it has been observed alive in the Atlantic.

Here is a plate of this animal from the HMS Challenger Expedition, which described it in 1889!!

This starfish, Neomorphaster, is better known to scientists, but seeing it alive like this? That's not something that happens often.

Our story begins with an overview of two unusual and quite tiny starfish! Some details:

Occur in Tasmania (Southern Australia)

Two species, Parvulastra vivipara and P. parvivipara occur on rocks and surrounding areas.

One of those starfish, P. parvivipara is among the world's smallest adult sea stars.

Indeed! Look how cute and tiny they are!

Image by Nuytsia@Tas

But the truth is that these tiny little starfish have all kinds of shocking sex secrets!1. Both Species of Parvulastra are self-fertilizing hermaphrodites. I have written about similar species in the same genus (Parvulastra) here. Yes, that's pretty much self explanatory. Individuals are simultaneously both male and female AND if need be they can fertilize themselves.

They typically have between 6 to 8 female gonads and 1 predominantly male gonad. However the amount of sperm present would not be expected in those species which are exclusively self-fertilizers-so SOME outcrossing (ie sex with other individuals) does occur.

So, eventually, those little baby starfishes have to leave the comfort of the mother's body cavity. This happens when they reach about 25-30% of the parent's body diameter.

The downside of having brooded juveniles is that they tend not to go very far from the adult. In other species, the larvae would be dispersed over wide distances but here, they are retained or crawl away, staying near the parent..

Eventually, they exit via openings in the abactinal body wall called GONOPORES.

Life is harsh and these starfish know it better than anyone. The gonads in these animals are pretty small which implies that food for the juveniles isn't really enough to keep them sustained on their own..

So, as soon as the brooded juveniles develop a mouth they begin feeding on their siblings in the body cavity! In the specimens examined several of the larger brood individuals, which contained traces of the smaller ones in their gut contents in addition to other observations..

Several possible reasons may motivate the departure of the smaller juveniles from the brood space. Temperature or any number of factors.

Byrne speculated on one reason that juveniles may vacate in order to avoid being fed upon by their larger siblings.. Here is a cartoon supplied by the Echinoblog Art Dept. which illustrates this notion (which to be honest was mentioned as only one sentence by Byrne in her paper).

Ultimately, then we see various brooded juveniles vacating the brood space via the gonopores (which flex and open) with the tiny juveniles emerging on the surface and eventually moving away...

Fr. Byrne 1996, Fig. 8b

Thanks to the intragonadal cannibalism however, sometimes you get a REALLY big one which continues to grow INSIDE the parent. Ultimately reaching a size at which it cannot physically escape on its own..

There was nearly a complete loss of genetic diversity among all populations of Parvulastra and given the very restricted geographic range of these species+ the very limited way they can disperse their juveniles across wide distances there's little potential for populations to expand.

Thus, these live-brooding species with little to no gene flow display a high risk of extinction

So, there is serious concern about these species to withstand any kind of temperature or climate shift. The populations of these live-bearing starfish species is pretty small and pretty restricted. Potentially any kind of abrupt habitat change could wipe out these starfish with these unusual life modes..

There is a natural and wonderful symmetry to many natural objects and echinoderms have always had a certain appeal to folks with artistic natures. Their skeletons are pentameral and often have no shortage of patterns and visually interesting processes. Go here to seem my SEM odyssey of the urchin test!

Sea urchins are no exception to this-and everyone I know who has ever found an intact sea urchin (or sand dollar) test on the beach is always delighted. A "test" is the name of a sea urchin skeleton. They don't have "shells".

Here's a nice example of a cidaroid sea urchin test. The spines attach to the "knobs" (called bosses) that are present on its surface.

sea urchin test by Rainy City

Today, I thought I would present some of the many delightful examples that many of these tests have found their way into the creative processes of the wonderful artists on the Internet! Then compare below with some examples of sea urchin tests with their own innate artful patterns!

Cidaroid Urchins a la Warhol! by Calypso985

A stunning underlit cidaroid urchin test by Mark Bolles

A neat repeating Urchin Spiral by Jeff Kreulan

"Red Tide" part of an art exhibit featuring urchins with a distinctive presentation. Pic by Selene Vomer

Amazingly, the patterns? ARE NATURALLY OCCURRING. Those are on the test under the spines and all of the other structures and skin on the surface! They don't disappear after the animal has died. They are ingrained in the mineral structure of the test.

Today is a "report from the field" by Jonathan Martin, a research associate at Simon Fraser University, who is among other things, an ROV pilot, diver and photographer. His pictures can be found at this Flickr stream here.

Martin has recently sent me a series of images and video that show a massive die off of the sunflowerstar, Pycnopodia helianthoides in the waters of British Columbia in 20-50 feet of water.

A picture of the sunflower star in a healthy state is above. Pycnopodia is a prominent member of the Pacific northwest intertidal/subtidal marine fauna. It boasts about 20-25 rays and can get to be quite large (about 2 to 2.5 feet across).

ALL pictures in today's post were provided by Jonathan (except where noted otherwise).

The Evidence: Images & Video

Here's a video transect made by Jonathan

See all that white stuff on the bottom?? Those are decaying, white tissues and ossicles from sunflower stars. You can see the fleshy remains all around the bottoms.

His direct observations (dated August/September 2013):

I just got back from a dive out in West Vancouver though, and there seems to be a huge mortality event of some kind with the animals, where they seem to waste away, 'deflate' a little, and then just... disintegrate. The arms just detach, and the central disc falls apart. It seems to happen rapidly, and not just dead animals undergoing decomposition, as I observed single arms clinging to the rock faces, tube feet still moving, with the skin split, gills flapping in the current. I've seen single animals in the past looking like this, and the first dive this morning I thought it might be crabbers chopping them up and tossing them off the rocks. Then we did our second dive in an area closed to fishing, and in absolutely amazing numbers. The bottom from about 20 to 50 feet was absolutely littered with arms, oral discs, tube feet, gonads and gills, the the extent where it was kind of creepy.

More pictures of Pycnopodia in various states of decay..

Partial remains of a disk and white, dead starfish tissues..

In some cases, arms were separated with tube feet still moving around

What makes this such a concern? OTHER starfish species in completely different lineages also seem to be affected. The sea star predator, Solaster dawsoni was also observed in various states of distress..

Solaster feeds on other starfish and does feed on Pycnopodia, so is there a connection?? Especially with the recent population explosion??

So What's Going On? So, there were a number of different ideas that buzzed through my head. Again, this is all SPECULATION on my part...

1. Is this related to the population explosion, observed almost 3 years ago?? Could the huge populations from 2010 be suddenly dying off? Famine? Disease? (see below) This would be an unusual (or at least poorly known) phenomena. I've seen Pycnopodia in aquaria live out long lives, so I don't think this is some kind of "natural causes" thing...

There are accounts of many sea urchins being decimated by various bacterial infections, such as Bald Sea Urchin disease but my skim of the literature suggests that there isn't anything known about similar diseases in sea stars. Most mass-mortalities of seastars have been associated with environmental changes- freshwater from rains, storm and wind, toxicity in the water from geological events and so on...

3. Why is it affecting other species? So we have one big Pycnopodia die-off. Why have all the Solaster stars ALSO been dying? One immediate answer might be that whatever toxic substance is in Pycnopodia has been fed upon by Solaster, resulting in further mortality. Or it could be in the water.. More data and observations are needed.

Have other species in completely different ecological regimes died?

SO FAR, this has been observed only in the British Columbia region. Hopefully, this is just an isolated incident and nothing that will be slowly moving in any other direction.

I'm not an ecologist or an invertebrate pathologist.. so maybe someone out there with an appropriately equipped lab will embrace this and seek out the answers? and hopefully whatever it is, won't be much more widespread..

This sparked some good academic discussion here which I can only hope will lead to some further insight into what is happening. One useful thing which came up was the mention of something that would be a good follow up to last weeks' report: Starfish Wasting Disease!

But what actually causes the disease?? Sadly, we are just beginning to understand it and so we don't actually know WHAT the causative agent is. Molecular tests for bacteria haven't confirmed anything.Could it be a virus? A fungus? Some strange combination thereof?

Its also unclear if it is the SAME agent at work in EVERY case. Different species? Different strains? Different diseases?

The symptoms of the disease have been documented widely: on the west coast of North America. From British Columbia down to the Gulf of California. But also in the Mediterranean and the North Atlantic coast of North America.

Nothing yet from the Southern Hemisphere.. Australia, New Zealand, etc.What Species Does It Affect?Wasting disease appears to be pretty widespread across MANY starfish groups. The symptoms of the disease have been observed as early as 1972 from the east coast of North America in the "common" starfish Asterias vulgaris (now called Asterias rubens, pic on the left)

In 1982, there was a mass die-off of Heliaster kubiniji in the Gulf of California, which was so severe that it led to local extinction in several areas where it had once been abundant. (Image ofAsterias by "misenus1", Image ofHeliasterby manzanita-pct)

Eckert's account in the Channel Islands however, documents the widest spread where it was recorded affecting TEN species of most commonly occurring sea stars! Not to mention three sea urchins, two brittle stars, and one species of sea cucumber!

Disease outbreaks in these species resulted in die-offs and significant population declines.

In our recent example with Pycnopodia, which looks very much like wasting disease, we saw not just Pycnopodia, but also the sun star- Solaster dawsoni..(pics by Jonathan Martin)

Solaster dawsoni feeds on sunflower stars..

Similarly, Allison observed the bat stars, Patiria miniata feeding on decaying Pisaster ochraceus. Can the disease be conveyed as food? Will we start to see greater spread?

But again, we don't know the actual agent of wasting disease. The symptoms might be something that happens in parallel as a result of several different agents.

Temperature! The Key to Wasting DiseaseEckert's paper speculated that warmer waters in the Southern California region accompanied the onset of wasting disease in the species they studied.

Amanda Bates & her team study studied Pisaster ochraceus in British Columbia and studied several variables and how they affected the disease.

Indeed, temperature turns out to be a very important factor in the spread of starfish wasting disease!

The graph below shows that the prevalence of the disease in starfish under experimental conditions is significantly higher under warmer conditions. This was also reflected by observations in the wild as they saw higher incidence of disease in the summer (June) than in August.

Figure 3 from Bates et al. 2009

One final and important observation that Bates and her team recorded was that the disease prevalence was higher in a protected inlet (GM=Grappler Mouth) versus an open wave-swept area (SB=Scott's Bay).

This highlights another aspect: What aspect of starfish in the protected inlet vs. the open area to the higher infection rate?

Aquaria, it was observed, also tended to show higher incidences of infection.

So, it appears there seems to be a good correlation with wasting disease prevalence and infection strength with higher temperature. Also being exposed to open ocean conditions vs. more enclosed conditions..

Starfish Wasting Disease in the Big Picture

1. Global Warming. If this disease and the ciliate castration parasite are both temperature dependent and we are seeing an across-the-board increase in ocean temperature, this could have significant or even profound effects on populations.

Higher rates of diseases and greater vulnerability to diseases affecting not just sea stars, but urchins, and other echinoderms could seriously impact populations of these species.

Ochre stars for example affect mussels and other animals in marine ecosystems that cover rocky intertidal bottoms. Sunflower stars are a major predator of everything from snails to sea urchins, and sometimes other starfishes.

Among this pantheon of photogenic and/or striking bunch of marine animals is a formidible polychaete worm- in the genus Eunice, also known as the BOBBIT WORM!

Here's video of this animal's remarkable prowess (more videos are here). These worms reach 3 m (6 FEET) long and are raptorial predators which use spring loaded jaws to capture their prey... One record holder indicates a worm which was nearly SIX meters in length when collected!

Yes. That's basically a worm the size of a large SNAKE with jaws to match!

This animal has been getting increasingly more exposure as various sites have been introducing marine invertebrates into their blogs and such. This is a good thing for those of us who study marine invertebrates. An animal once known only to specialists is now becoming accessible to everyone..

I've noticed increasingly however that many of these newer accounts of the Bobbit Worm are missing something.

Part of my time there involved my helping two of the curators, Gary Williams and Terry Gosliner, who were experts in soft corals and nudibranchs, respectively, identify starfish for their upcoming book on Indo-Pacific animals.

During the research for the book, Gary and Terry returned from a trip to the research dive to the Philippines where they spied a crazy thing. A great story that was told one brisk Friday in San Francisco!

(story recreated here with new images) A GIANT worm with spring loaded jaws the size of a SNAKE jumped OUT of its burrow and grabbed a freakin' FISH while it was swimming by! Images below by Eunice Khoo (Mer Mate)

Image by Jason Isley

I didn't believe it. But there it was.

Bear in mind. Digital cameras were just becoming available. HD underwater Video was nowhere nearly as good as it is today. YouTube was non-existent. The WWW was around but didn't have the size and scope it was today. Most people didn't even KNOW polychaetes were any larger than about a foot long at most. If you saw polychaetes in a coffee table book or marine biology photo magazine you were pretty lucky. The only people who ever saw these huge monstrous worms were divers, scientists and maybe the locals.

The specimen had been identified to genus, Eunice sp. but not to species (I'll explain more below), but Terry Gosliner felt that it a special beast worthy of distinction! And hence the name... (excerpt below from their book)

Since its original use, the common name has been largely applied to almost any large, predatory polychaete, which most untrained "citizen scientists" such as divers, aquarists, etc. are generally unable to distinguish.

For example, is this a "proper" Bobbit worm? It looks close, but lacks the same kind of jaws. So, probably not. But its not unsual for big, attractive polychaetes to get labelled "Bobbit Worms"

This for example is another species of Eunice (I think..) but is it a "Bobbit worm"?

The species shows a LOT of differences in body form all around the world. Do these differences represent different species? Or just minor changes in body form in ONE species??

Is this the SAME species ALL OVER the world?

The 'Proper" Bobbit Worm was a species originally observed from the Philippines and may or may not be the same species frequently observed in Indonesia and thereabouts in videos and such. In fact, if you read the description above, it was originally thought to be a new species and still may be!

This paper by Anja Schutlz further outlines methods that we might further understand the questions surrounding the question "What species is the Bobbit worm??" Population genetics of the world populations and further sampling of species from around the world.. (as well as people who can identify them correctly).

Beautiful photo by Eric Cheng!

So, conceivably we have not even SEEN the TRUE Bobbit Worm (i.e. the animal originally named as such) as a proper species yet!

But because the common name "Bobbit Worm" seems to have become rather liberally applied to most large eunicid worms, its likely that name will stick. Not just to Indo-Pacific eunicids but to others..

In a cold-temperate water genus of brittle stars, called Ophiothrix which you can find in Europe, and in the cold-temperate waters of both the Pacific and Atlantic coasts of North America, they frequently occur in very dense, very abundant numbers!

How dense? One paper by G.F. Warner found that the mean population of O. fragilis in the British Islands was found to cover 23% of the ground in some areas, with a mean population density of 1330 indivdiuals per square meter!!

For example, here's a couple of nice shots of dense Ophiothrix fragiis beds them from Scotland (and thus the North Atlantic!)

Image by MatYts

Image by hsacdirk

This one is a pic of a different, Pacific species but it is a tighter shot and it gives you an idea of how the animals are positioned and what they look like individually.. Note that their arms are ALL extended up into the water!

Image by echo&dust

Spines are ALL over these things.. but they aren't necessarily for defense!

Image by hsacdirk

Here is a nice video of Ophiothrix in Santa Barbara, where they completely carpet the bottom. Or in the lower video, from deeper water in Monterey Bay.

But What about in the Deep-Sea???I said TWO kinds of brittle star carpets! so here ya' go... Ophiuroids are crazy abundant in the deep-sea as well.. comprising a HUGE amount of the biomass living on the bottoms!

The story is in many ways similar to those at shallow water depth.. juveniles sense the presence of other adults and settle.. but arms are not upheld in the water as readily... What could they be doing down there?

Many have indicated that they are possibly detritivores. Feeding on dead stuff and other organic material as it falls to the deep-sea bottom... as seen here (and fighting amongst each other for food!)

One of the things I find fascinating about sea cucumbers is that they're basically a section of intestine, including the mouth and the anus which has evolved to live on its own. We sometimes think of animals by their most prominent features.. jaws in sharks, eyes in insects...

But Sea cucumbers are basically a big living gut! and have developed many unusual ways of living with this body plan..

Image by WhiteBeachDivers

It should not be so unusual that the openings to this "living gut" are especially important. The mouth of course, we see used in feeding but in sea cucumbers, of particular significance seems to be the importance of that second, most prominent opening.. the ANUS!

Awesome image by PacificKlaus

This is of course, where inorganic sediment is defecated after the animal has eaten and removed the organic material that fuels its diet...

But SO many other biological functions in sea cucumbers are now being observed in sea cucumbers..

Interestingly, there are also photo accounts of these shrimps living around sea cucumber anuses.. perhaps to take advantage of other organic material?

Image by Eric Francis

Here are more shrimp+crab anal assemblages...

Image by Swaflyboy

Incidental occurrence? or preference?

Image by ScubaSchnauzer

This shrimp seems to have found itself completely embedded in sea cucumber anus!

Image by Prillfish

Many questions-what do the crabs and shrimps get out of this? Are they species specific? Is this really a region specific habitat? Or do they just use the whole animal as a house with the anus as a door?

Why Should We care? With all the media picking up the story and carrying it around to multiple outlets, at some point someone will get beyond the "weird news" twist that has been put on the articles and ask "So What?" Here are 5 reasons I think understanding why this die-off MUST be studied.1. An Endemic Starfish Fauna.

Basically, one of the important facts was that all of the asteriid starfishes in this area, including Pycnopodia (the sunflower starfish), Pisaster (the ochre star), Evasterias, Leptasterias, etc. on the Pacific coast of North America are ENDEMIC TO THE COAST.

That means, you could see a starfish which resembles Pycnopodia in Australia or Mexico and it will have LESS relationship to Pycnopodia than Pycnopodia has to Pisaster!

Bottom line: You won't find these starfish species anywhere else in the world. These animals are an important part of the marine ecology of the Pacific coast of North America.2. Aesthetic & Cultural History

Image by sjonnie van der kist

“What do they find to study?” Hazel continued. “They’re just starfish. There’s millions of ’em around. I could get you a million of ’em.”“They’re complicated and interesting animals,” Doc said a little defensively.

If this isn't a communicable disease per se but is instead more of a series of symptoms related to poor or changing environmental factors, which activates/corrupts/modifies that fauna, THAT could be a concern which leads us to our next point...

5. Widespread Ecological Impact. Here's the million dollar issue.. What happens if diseases change abundance or remove these species from their habitats? WHAT HAPPENS? What COULD happen?

Image by Phil Williamson

Image by Daniel Johnson

The thing is, that BOTH of these species occupy important ecological positions. As mentioned earlier, Pisaster is a keystone species. The presence or absence of a keystone species in an ecosystem can dramatically change the interactions of that ecosystem.

For example, Ochre stars (Pisaster ochraceus) removed from the intertidal would likely result in a significant overgrowth of mussels and other invertebrates which ochre stars typically feed upon. Mussels might come to dominate an ecosystem and prevent other animals from inhabiting that area. There could be a cascade of other consequences of course...

What is perhaps most concerning is how MANY starfish species seem to be affected. Many of their ecological roles are poorly understood but are likely to be important. The effect on the ecosystem is likely to be significant.

Thanks to many discussions at Science Online Oceans this past weekend for discussions that inspired this post!

PARIS! I've just arrived and hard at work with my colleagues at the Museum national d'Histoire naturelle! But this week has been crazy. Wi-fi down, taking care of last minute projects and so forth on top of travel and jet lag.

So this week the blog is about a curious set of street art I've seen. OCTOPUSES all around Paris!

These are often painted or posted surreptitiously around Paris in strange corners and rarely travelled nooks around the city. Based on the arm length and overall appearance they appear to most closely resemble the "dumbo" octopus -something like Grimpateuthis or Opisthoteuthis but I'm pretty sure the artist has mainly taken the image from his own imagination...